As it is well known in this specific technical field, non volatile memories, and particularly electrically programmable and erasable flash memories, comprise cell matrices, each matrix being an information storage unit. It is also known that, to ensure an optimum memory operation, it is necessary that the cells are adjacent to each other, thus ensuring a continuous addressing area.
It is possible that a cell, a set of cells or whole hierarchical cell structures (rows, columns, matrix sectors) may not operate correctly, thus making the whole memory unusable. To overcome this problem the use of redundancy resources has been suggested, i.e. the realization of memories comprising a greater number of cells or cell structures (rows, columns, sectors) than the memory nominal capacity, i.e. than the cells being strictly necessary to ensure a predetermined memory nominal capacity.
It is therefore possible to replace non-operating sectors of the memory matrix with the redundancy resources, allowing memories otherwise considered unusable to be recovered. Although advantageous under many aspects, and substantially corresponding to the scope, this first technical approach has a major drawback described below.
The insertion of redundancy resources leads to the construction of memories with a greater area than the area being strictly necessary, independent of whether they are defective or operating, and this negatively affects production costs.